3 research outputs found
Thermal and Photochemical Ring-Bromination in Naphthyl‑, Naphthdiyl‑, and Dicarboximideperyl-Platinum Complexes
No full textBrominated
polycyclic aromatic compounds are important synthons, but their synthesis
can be difficult. Herein, we report that PtÂ(IV) centers σ-bonded
to naphthalene and a dicarboximideperylene activate the ring systems
to selective thermal and photochemical bromination. Thus, <i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>(Br)<sub>3</sub>Â(4-bromo-1-naphthyl)
and Br<sub>2</sub> give <i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>(Br)<sub>3</sub>Â(7,4-dibromo-1-naphthyl). Introduction
of a second PtÂ(IV) center is achieved by double oxidative addition
of 1,4-dibromonaphthalene to 2PtÂ(PEt<sub>3</sub>)<sub>4</sub>. Bromination
of [<i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>Br]<sub>2</sub>Â(1,4-naphthdiyl) yields [<i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>(Br)<sub>3</sub>]<sub>2</sub>Â(1,4-naphthdiyl),
which further brominates on the ring to give [<i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>(Br)<sub>3</sub>]<sub>2</sub>Â(6,7-dibromo-1,4-naphthdiyl).
Photoreduction of the PtÂ(IV) centers with 1-hexene gives first mixed-valent
[<i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>(Br)<sub>3</sub>]Â[<i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>(Br)]Â(6,7-dibromo-1,4-naphthdiyl)
and then [<i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>Br]<sub>2</sub>Â(6,7-dibromo-1,4-naphthdiyl). Photoreduction of <i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>(Br)<sub>3</sub>(PMI)
(PMI = <i>N</i>-(2,5-di<i>-tert</i>-butylphenyl)Âperylen-3-yl-9,10-dicarboximide)
without 1-hexene slowly gives ring-bromination at the PMI 12-position.
HOTf treatment cleaves the Pt–PMI bond to give 12-bromo-<i>N</i>-(2,5-di<i>-tert</i>-butylphenyl)Âperylene-9,10-dicarboximide.
The reaction chemistry indicates that the PtÂ(IV) center is equivalent
to a bulky, electron-donating group for the naphthalene and PMI ring
systems
High Quantum Yield Molecular Bromine Photoelimination from Mononuclear Platinum(IV) Complexes
No full textPtÂ(IV)
complexes <i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>(R)Â(Br)<sub>3</sub> (R = Br, aryl and polycyclic aromatic fragments) photoeliminate
molecular bromine with quantum yields as high as 82%. Photoelimination
occurs both in the solid state and in solution. Calorimetry measurements
and DFT calculations (PMe<sub>3</sub> analogs) indicate endothermic
and endergonic photoeliminations with free energies from 2 to 22 kcal/mol
of Br<sub>2</sub>. Solution trapping experiments with high concentrations
of 2,3-dimethyl-2-butene suggest a radical-like excited state precursor
to bromine elimination
High Quantum Yield Molecular Bromine Photoelimination from Mononuclear Platinum(IV) Complexes
No full textPtÂ(IV)
complexes <i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>(R)Â(Br)<sub>3</sub> (R = Br, aryl and polycyclic aromatic fragments) photoeliminate
molecular bromine with quantum yields as high as 82%. Photoelimination
occurs both in the solid state and in solution. Calorimetry measurements
and DFT calculations (PMe<sub>3</sub> analogs) indicate endothermic
and endergonic photoeliminations with free energies from 2 to 22 kcal/mol
of Br<sub>2</sub>. Solution trapping experiments with high concentrations
of 2,3-dimethyl-2-butene suggest a radical-like excited state precursor
to bromine elimination
